Buu N T
Laboratory of the Autonomic Nervous System, Clinical Research Institute of montreal, Quebec, Canada.
Biochem Pharmacol. 1989 Jun 1;38(11):1787-92. doi: 10.1016/0006-2952(89)90413-9.
In this study, the accumulations of dopamine (DA) and norepinephrine (NE) were measured in the brain tissues and in the synaptic vesicle fractions prepared from whole brain of control rats and rats injected with L-DOPA. In the normal rat brain, a 3-fold increase in DA following L-DOPA administration was followed by a small, but not significant increase in vesicular DA, indicating a restricted vesicular uptake of exogenous DA. At the same time, NE in the vesicular fraction and in the whole brain tissue did not change, suggesting a possible link between DA vesicular uptake of DA and brain NE. However, in rats pretreated with alpha-methyl-p-tyrosine, which significantly (P less than 0.05) reduced DA and NE levels in brain tissues and in the synaptic vesicles, L-DOPA administration led to a significant increase in vesicular DA (P less than 0.05), suggesting that catecholamine depletion may result in greater vesicular uptake of cytoplasmic DA. The increase in vesicular DA was accompanied by increases in tissue and vesicular NE, underscoring again the existence of a link between vesicular uptake of DA and brain NE following L-DOPA administration. The results also demonstrated a large increase in 3,4-dihydroxyphenylacetic acid (DOPAC) following L-DOPA, in the brain tissues but not in the synaptic vesicle, indicating that monoamine oxidase activity is confined to the cytoplasm.
在本研究中，测定了对照组大鼠和注射左旋多巴的大鼠脑组织及从全脑制备的突触小泡组分中多巴胺（DA）和去甲肾上腺素（NE）的蓄积情况。在正常大鼠脑中，给予左旋多巴后DA增加了3倍，随后囊泡DA有小幅但不显著的增加，这表明外源性DA的囊泡摄取受限。同时，囊泡组分和全脑组织中的NE没有变化，这提示DA的囊泡摄取与脑NE之间可能存在联系。然而，在用α-甲基-对-酪氨酸预处理的大鼠中，脑组织和突触小泡中的DA和NE水平显著（P<0.05）降低，给予左旋多巴导致囊泡DA显著增加（P<0.05），这表明儿茶酚胺耗竭可能导致细胞质DA的囊泡摄取增加。囊泡DA的增加伴随着组织和囊泡NE的增加，再次强调了给予左旋多巴后DA的囊泡摄取与脑NE之间存在联系。结果还表明，给予左旋多巴后，脑组织中3,4-二羟基苯乙酸（DOPAC）大幅增加，但突触小泡中未增加，这表明单胺氧化酶活性局限于细胞质中。
